This invention relates generally to transmissive screens, and more particularly to transmissive screens suitable for use in rear projection systems.
Rear projection screens are generally designed to transmit an image projected onto the rear of the screen into a viewing space. The viewing space of the projection system may be relatively large (e.g., rear projection televisions), or relatively small (e.g., rear projection data monitors). The performance of a rear projection screen can be described in terms of various characteristics of the screen. Typical screen characteristics used to describe a screen""s performance include gain, viewing angle, resolution, contrast, the presence of undesirable artifacts such as color and speckle, and the like. It is generally desirable to have a rear projection screen that has high resolution, high contrast and a large gain. It is also desirable that the screen spread the light over a large viewing space. Unfortunately, as is described more fully below, as one screen characteristic is improved, one or more other screen characteristics often degrade. For example, in order to increase the screen gain using the same overall structure, one must decrease the viewing angle over which the screen is readily observable. As a result, certain tradeoffs are made in screen characteristics and performance in order to produce a screen that has overall acceptable performance for the particular rear projection display application.
Thus, there remains a need for screens that have improved overall performance while meeting the minimum performance criteria necessary for the rear projection display application in which the screen is used.
Generally, the present invention relates to projection screen assemblies. In particular, the invention relates to projection screen assemblies that include one or more birefringent retarding layers and one or more polarizing layers. The retarding and polarizing layers reduce the unwanted reflection of ambient and image light.
In one embodiment, a screen assembly includes a dispersing layer having an input side to receive light from a light source and a first retarding layer disposed to alter the polarization of the light transmitted by the dispersing film. A first polarizer substantially transmits light received from the first retarding layer in a first polarization state and absorbs light received from the first retarding layer in a second polarization state orthogonal to the first polarization state.
Another embodiment of the invention is a projection system having a screen and an image projector projecting an image having a first polarization state onto the screen. The screen includes a light dispersing element, a first retarding layer, and a first polarizing layer. The first retarding layer is oriented to convert the image from to a transmission polarization state substantially parallel to a transmitted polarization direction of the polarizing layer.
Another embodiment of the invention is a screen assembly, with dispersing means, first birefringent retarding means disposed to receive light from the dispersing means; and first polarizing means disposed to receive light from the second birefringent retarding means.
Another embodiment of the invention is a screen assembly for displaying an image having a first polarization state. The screen includes a first polarizing layer oriented to substantially transmit light in the first polarization state and a first retarding layer disposed to receive light from the first polarizing layer. A light dispersing layer is disposed to receive light from the first retarding layer.
The above summary of the present invention is not intended to describe each illustrated embodiment or every implementation of the present invention. The figures and detailed description that follow more particularly exemplify these embodiments.